The present invention relates to a method of specifically releasing a one or more members of a sub-group of objects from an entity, a method of detecting a subject's disease by detecting one or more members of a sub-group of biological entities indicative of the disease and a method of isolating one or more members of a sub-group of objects from a group of objects.
In modern research, the availability and selection of a suitable assay is a decisive step. Therefore, a multitude of different assay designs has been developed. In health care, assays may be used to detect particular chemical, biochemical or biological compounds or entities, i.e., proteins, nucleic acids, ligands or cells, which have been correlated or are associated with various disease conditions. In the field chemistry or pharmacy, screening assays for the identification of targets are particularly suitable, as they usually allow for the screening of multitude of compounds in one assay design and allow for rather quick identification of new, valuable chemical, biochemical or biological compounds or entities. Many of these tests are based on the selective binding to a target of interest. In general, assay designs can be sub-classified into between homogenous assays and heterogenous assays.
Homogenous assays are those not involving a separation step. Homogenous assays may be used if the target differs from other compounds and can be detected based on this difference. An example would be an assay including a labeling of a target entity. If the labeled target entity behaves differently than a non-labeled non-target entity, no separation step would be required.
One possibility of detecting targets in a homogenous assay is by proximity assays. Proximity assays are based on the binding of a “detecting agent” to a target. Upon the binding, a signal is generated due to the proximity of the target to the detecting agent. For example, in scintillation proximity assays or fluorescence resonance energy transfer (FRET) assays, energy is transferred from the target to the detecting agent. In other formats, a catalytic reaction may be allowed (e.g. by the proximity of an enzyme to its substrate).
Heterogenous assay require a separation step. In heterogenous assay formats, target entities are usually separated form non-target entities and detected thereafter. Therefore, heterogenous test require that at least one component of the test is attached to an entity or support, preferably a solid support. Accordingly, the term “heterogeneous assay” as used herein refers to an assay method, wherein at least one of the reactants in the assay mixture is attached to an entity or support allowing for separation, such as a solid support.
Homogeneous are most desired from an operational standpoints since the entire reaction and an addition of reagents for the performance of the assay, take place in a single solution along with the final detection step. Accordingly, mechanical manipulations, which are time-consuming and can cause errors, are avoided; however, the technical aspects of developing such an assay with the desired sensitivity are substantial. In contrast, numerous assays are performed on a heterogeneous basis in that certain steps are performed in one solution which includes some type of solid phase material. The reaction to be detected takes place on the solid phase and is then followed by a separation step, whereby unreacted components, and thus contaminating influences, may be effectively removed. The result is generally a higher level sensitivity at the expense of additional mechanical manipulations.